Zircon refractory and method of making it



Patented Jan. 4, 1944 ax arm METHOD or ZIRCON REFRACTO MARIN GIT Robert Karl Smith, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York No Drawing. Application December 20, 1941,

I Serial No. 423,837

10 Claims.

This invention relates to refractory compositions of general utility which are alsosuitable for use in contact with molten glass and more particularly to refractory compositions composed wholly or largely of refractory zirconium material such as zircon (zirconium silicate), or zinconia (zirconium oxide).

The object of the invention is to increasethe corrosion resistance of zirconium refractories.

Another object of the invention is to produce a refractory composition which is more resistant than prior refractory compositions to corrosive attack of molten lime glass, that is, glass containing substantial amounts of lime and/or other second group oxides.

Another object is to cause maximum shrinkage of a zircon or zirconiavrefractory during the firing thereof and therebyto give the finished composition a very close and dense structure having low porosity. v

To these and other ends, which may become apparent as the description proceeds, the invention comprises amongvits features the preparation of refractory compositions composed of zircon or zirconia to which are added minor and specific amounts of metallic oxides not-heretofore used in such refractories, someof which have the unusual effect of increasing the corrosion resistance of the refractory body while others have a mineralizing effect or the. ability to promote shrinkage on firing. I

I have found that the addition of about 1% of vanadic oxide (V205) to a refractory consisting of zircon will substantiallylncrease its resistance to corrosion by molten lime glass although the shrinkage on firing is not thereby substantially increased over that of the pure zircon refractory, That this effect depends upon a critical proportion of V205 is shown by the fact that amounts of V205 less than and more'than 1.2%, instead of increasing. the corrosion resistance-actually decrease it; V

Corrosion" resistance is determined by vertically inserting a molded bar of the refractory into a batch of glass "cullet contained in a crucible, the bar being 1 cm. square in cross section and sufficiently long to project above the surface of the glass when the latter is molten. The crucible and its contents are heated to melt the glass and the whole is held at about 1550 C. for fifteen hours. At the end of this time the crucible is cooled and the depth of the corrosion of the refractory bar at the metal line is measured. By means of this test the depth of corrosion by lime glass of a bar composed of pure zircon is 5 mm., thatis, the bar is completely severed, while a similar bar containing about 1% of V205 is corroded to a depth of only v I have further found that the. addition: of about 1% of an oxide of iron, cobalt, nickel or manganese to pure zircon or zirconia refractory causes a shrinkage of the body when it is fired to 1550 C., which is substantially greater than the shrinkage of a similar body of pure zircon or zirconia alone under like conditions. 'With -i% of such oxide the maximum shrinkage effect is ob tained and the use of higherpercentagescauses no further shrinkage. The shrinkage is determined by molding a bar of the refractory material approximately 15 cm. x 2cm. x 1 cm., making two marks of reference thereon at a distance of 10 cm. from each other,rfiring the bar up to 1550-C. and measuring the distance between the reference marks after firing. The decrease in the distance between the marks of reference is calculated in terms of shrinkage in inches per inch of refractory and can also be expressed as percent shrinkage. The following table shows the percent shrinkage of the various compositions which -I have found to be effective as compared with pure zircon and pure zirconia.

Shrinkage Composition g gzf 1550 C.

Percent 1 are zircon 6 Pure zirconia 4 99% zircon, ligl enh. 12 99% zircon, 1% Q9203 ll. 2 99% zircon, 1% b11 03. 9. 4 99% zircon, 1% MnOz. 9. 2 99% zircon, l% V20i.. 5-6 98 7 zircon 1% "20s, 8201 9 Q9 0 zircoma, 1% F9203 7. 5

" AIthOiIgh V205 does not substantially change the shrinkage of the refractory, it greatly increases its resistance to corrosion as shown-above.

The oxides ofrir'on, cobalt,-nickel and; manganese cause a substantial increase in shrinkage. thereby giving the refractory a more dense or less porous structure. Iron oxide, which is most effective in this respect, produces a shrinkage of about 12% in zircon refractory which in this composition results in about 9% porosity as compared to about 25% porosity for the pure zir con. In the zirconia refractory the increased shrinkage caused by the addition of iron oxide prevents the formation of cracks on firing. Such cracks are a particularly objectionable characteristie ofairconia refractories and have hithertopreventeditsuseexceptinsmallsiaedbodies. Ihenthese shrinkage promoting oxides are introdnced into aaircon refractory together with about 15 of VaOs the corrosion resistance is furtherincreaaedbytheresultingdecreasein porosity. particularly when R; is used with "VaOuaeahuwn.

-Iillpaaaa.screenof335meshuperinchisa eommonproductonthemarketand the above rccitedeflectivemodifyingoxidescan alsobe .teriaharepartlcularlyadaptedformyprocess andareeminentlyfsuited formolding by the psuce-hnownssiipcasting. oonsequentlrin thepsaeticeotmyinventionthe-reiractory batch ofmchmateriaisispreferablyformedintoaslip andmoldedhycastingtheslipintheusualmannerinaposmmolmasiaillmtratedbythefol lo Ilngexa-ple.

.75 In. (34 liters) at .water and .12 ounce of -sodlmsilicatesohrtion (sp. 51.31) aremixed uniformly with 5. ill of finely divided zircon (32inch). The sodium silicate functions as a defloccnlant and,aaiswellknown,substantially decreaaestheamountofwaternecessar'ytoform aalip,therehyfacihtatingthedryingofthecast The above recited quantity" of water amounts to appsoaimateiyiSccperiOOgramsofdrybatch-and shouldnotexceed about 17 cc. per 100 grams of batch. The desired modifying oxide oroxides, for example, about .05 lb. or vanadic acid and abouhfilhofferrieorideJsthenaddeda-ndthe wholeislaltatedimtiluniforminconsistency. the dip is thsnready for casting in the usual 'nnnerhythetechniquewhichiswellknownin tlusart Arterthecastbodyhaspmperhsetitis remondfromthemdriedslowlyandflred.

'l'he'nseparatlonofasirconiarefractorybody hiaccordaneewiththeinventioniaaccomplismd in the same manner as the preparation of a zircon refractory. On account of its greater density, however, zirconia will require only 11 cc. of water per 100 grams of dry batch to produce a slip by the above recited procedure.

Since the process permits the molding of various intricate shapes which would be difllcult to accomplish by ramming or hand molding methods, the resulting bodies on account of their low porosities when fired can be used for a variety of purposes requirlng'contact with molten glass:

They are particularly useful in contact with moltenlimeglassonaccountoftheirenhanced resistance to the corrosive action of such glas.

The introduction of iron oxideintothe refractory compositions of this invention is not obiectionable from the standpoint of discoloration of glass melted in contact therewith because the ultimate iron content is substantially no greater than that of ordinary reiractories due to the initial purity of the zirconium materials Thereforeonaccountoftheincreasedresistance tocorrosion of my refractories, glass melted in contact therewith is actually less discolored by iron than in ordinary refractory bodies.

I claim: p

1. A refractory composition comprising a maioi'v proportion of refractory zirconium material and about 1% of an oxide of vanadium 2. A refractory composition comprising a major proportion of zircon and about 1% of vanadlc oxide.

3. A refractory composition comprising over 98% of zircon and 0.5% to 1.2% of vanadic oxide. 4. Arefractory composition comprising a major proportion of zircon, about 1% of vanadic oxide, and a small percentage of ferric oxide.

5. A refractory composition comprising a major proportion of zircon, about 1% of vanadic oxide and a sinall percentage of cobalt oxide.

6. A refractory composition comprising a maJor proportion of zirconia and about 1% of vanadic oxide.

7. A refractory composition comprising a maior proportion of aircon, about 1% of vanadic oxide and about 1% of ferric oxide.

8. A refractory composition comprising a major proportion of zircon. about 1% of vanadic oxide and a small percentage of manganese oxide.

9. The method of making a refractory body suitable for use in contact with molten glass, which includes forming a slip comprising a major proportion of zircon, not more than about 17 cc. of water per 100 grams of solids, and about 1% of V205. molding the slip to form a body and firing the body at about 1550 C.

10. The method: of making a refractory body suitable for use in contact with molten glass, which includes forming a slip comprising a major proportion of zircon, not more than about 17 cc. of water per 100 grams of solids and about 1% of V20: and about 1% of moi. molding the slip to iormabodyandilringthebodyatabout 15500.

xsm. sun-n.

CERTIFICATE OF CORRECTION.

January 1;, 19%.

Patent No. 2,558,209.

ROBERT KARL SMITH.

It is hereby certified that error appears in the printed specifi cation of the above numbered patent requiring correction as follows: Page 2, first column, line 14.5, for (5h liters)" read (.'5l4.-1iters); and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the ease the Patent Office. I

Signed and sealed th is 28th day of March, A. D. 191 1;.

' Leslie Frazer (Seal) .Acting Commissioner of Patents. 

